1. Field of the Invention
The present invention relates to devices used to implant medical devices within a patient's vasculature.
2. Description of Related Art
It is known to deliver various implantable medical devices to a patient's vasculature. Typically, an implantable device is delivered to a treatment site (such as coronary artery, carotid artery, etc.) by locating the device near the distal end of a suitable catheter. The catheter can then be percutaneously introduced and guided to the deliver site where the device is then delivered.
Known implantable medical devices include, for example, stents and stent grafts (hereinafter collectively “stents”). Stents can be loaded on a balloon and delivered to the treatment site by inflating and then deflating the balloon. After balloon deflation the catheter can be withdrawn, leaving the stent implanted at the treatment site.
Another form of stents include the known “self-expanding” stents. Such stents are loaded onto the distal end of a catheter and delivered to the treatment site in a compressed state. Typically the stent is held in the compressed state by an outer sheath or tubular member. To deliver the stent the outer sheath, or tubular member, is, typically, withdrawn proximally along the catheter, thus allowing the stent to self-expand.
One means for withdrawing the sheath or tubular member is to provide the sheath or tubular member with a deployment line that extends proximally for the length of the catheter so that the physician can grasp the deployment line by hand. Upon locating the stent at the delivery site, the physician then slowly pulls back the deployment line, thereby gradually removing the sheath or tubular member and, thus, allowing the stent to self-expand.
A further means for withdrawing the sheath or tubular member includes providing the sheath or tubular member with a deployment line that extends proximally along the length of the catheter and into a suitable hand-held device. The deployment line can be retracted by operating a suitable mechanical device, such as that disclosed in US Patent Application Publication Number 2004/0006380 A1, in the names of Buck, et al. The device disclosed in the Buck et al. document includes a tubular member compressing the stent. The tubular member is capable of being retracted at a constant rate by rotating a knob at a constant rate. As the tubular member is retracted, the stent self-expands and is thus deployed.
One potential problem with the above-described delivery systems is that while retracting the outer sheath or tubular member at a relatively constant rate, it is common for the self-expanding stent to jump or slip out distally of the sheath or tubular member, thus causing poor stent placement or perhaps damage to the patient's vasculature.
Accordingly, it is a purpose of the present invention to overcome such shortcomings by providing a device that will allow for more accurate placement of implantable devices.